The present invention relates to stick-type antiperspirant compositions. More particularly it relates to improved gel-type antiperspirant sticks, a method for their manufacture and also to methods for treating or preventing perspiration and malodor associated with human underarm perspiration.
There are three main types of such stick formulations: compressed powder sticks, gel sticks, and wax sticks. While each of these formulation types may have advantages in certain use situations, each also has disadvantages. For example, compressed powder sticks are often brittle and hard, and leave a cosmetically-unacceptable dust upon application. Gels, while offering very good aesthetic characteristics, may be unstable due to interaction of the soap gelling agents typically used to solidify such sticks with the stick's "active" material (e.g., the astringent metallic salts used in antiperspirant sticks). Wax-based formulations can also yield cosmetrically-unacceptable products due to such factors such as hardness, greasiness, and stickiness. The opacity of such wax sticks, and the residue created in their use, may also be aesthetically undesirable.
Many stick formulations have been described in the literature which attempt to maintain the desirable cosmetic and aesthetic attributes of gel sticks, while minimizing their disadvantages. For example, antiperspirant gel sticks, using dibenzaldehyde monosorbitol acetal (herein "DBMSA") as a gelling agent, are described in U.S. Pat. No. 4,154,816, Roehl, et al., issued May 15, 1979, U.S. Pat. No. 4,346,079, Roehl, issued Aug. 24, 1982, and U.S. Pat. No. 4,518,582, Schamper, et al., issued May 21, 1985. Deodorant sticks using DBMSA are described in Japanese Pat. No. 50/52,007, published Apr. 8, 1975. Nevertheless, it has been found that such DBMSA sticks, while avoiding the use of soaps, may produce products with aesthetically unacceptable stickiness. Further, these sticks have relatively poor efficacy and contain high levels of ethanol which leads to skin irritation. This high level of ethanol also leads to shrinkage and weight loss of the packaged antiperspirant gel stick due to the volatility of ethanol.
The gel sticks of the prior art require very high processing temperatures as well as short active/DBMSA contact time which leads to product instability and to processing difficulties in large scale product manufacture. DBMSA is unstable in the presence of acid salts (such as antiperspirant actives). This instability is accentuated at high processing temperatures. The gel sticks of the present invention can be manufactured at lower processing temperatures, thereby allowing for longer active/DBMSA contact time, thereby producing a much more stable and satisfactory product.
Further, while the prior art teaches the addition of basic metal salts for stability, the present invention additionally provides a gel matrix of decreased polarity which significantly enhances the stability of the final product. The solid get sticks of the present invention provide very stable antiperspirant gel stick compositions with good efficacy as well as excellent cosmetics and aesthetics which are further characterized by their ease of manufacture.
It is therefore an object of the present invention to provide antiperspirant gel sticks which have good antiperspirant efficacy. It is still a further object to provide optically clear or translucent gel sticks which are cosmetically acceptable. A still further object of the present invention is to provide gel sticks which are stable and easy to formulate and manufacture. A still further object is to provide gel sticks which are non-sticky. A still further object is to provide gel sticks which contain relatively low levels of ethanol to minimize skin irritation, stinging and burning.
These and other objects of the present invention will become readily apparent from the detailed description which follows.
All percentages and ratios used herein are by weight unless otherwise specified.